The film begins with waves crashing against a shore. Washed up on the beach is a man named Dom Cobb, who sees two children playing in the waves next to him. An armed Japanese security officer looms over Cobb and calls up to his partner, stationed at a house nearby. In the house’s ornate dining room, the guards tell an elderly man named Saito that Cobb was found with only a handgun and a small spinning top. The guards drag Cobb in and seat him at the table. Saito asks Cobb if Cobb is there to kill him, and mentions that he recognizes the top as belonging to a man he met in a dream.
Suddenly, Cobb is dressed in a full suit at the table, joined by a business partner named Arthur. Saito also looks decades younger. Cobb declares that the most resilient parasite is an idea. Cobb and Arthur explain that, in a dream state, thoughts are vulnerable to theft, and that they alone know the “tricks” to prevent their unwanted “extraction.” Saito says he will consider the proposal and adjourns to a party. The room begins to tremble. In an apartment elsewhere, Cobb gazes at his watch as a series of explosions rock the streets outside. A man named Nash walks through the apartment, where Mr. Saito and Arthur are revealed to be connected to a device, sound asleep.
Back in the dream, Arthur tells Cobb that Saito is suspicious, but Cobb disagrees, telling Arthur that Saito’s secrets are in a safe. Cobb approaches a dark-haired woman named Mal at the party, who is contemplating jumping off a bridge. Cobb tells Mal that although he and the children miss her, he cannot trust her. After rappelling down the side of Saito’s estate, Cobb executes two guards with a silenced pistol and finds Saito’s safe, pocketing an envelope inside. He is discovered by Saito and Mal, who have taken Arthur hostage. Cobb disarms himself and Saito demands the envelope. Cobb hands it over and asks Saito if he “knew all along” or if Mal told him. Saito asks whether he is referring to the theft, or the fact that they are all asleep.
Saito asks the name of Cobb’s employer, and Mal points the gun at Arthur, explaining that although killing Arthur would simply wake him up, she can still inflict pain. Mal shoots Arthur in the foot, suggesting they are in Arthur’s dream. Cobb dives for his gun and kills Arthur, who wakes up in the apartment and tells Nash the dream is collapsing. As the dreamworld begins to implode, Saito realizes that his envelope is a decoy, and that Cobb has the real one. In the apartment, Arthur tries keeping Saito asleep, but Saito awakens and points a gun at Arthur. Nash gives Cobb what Arthur calls a “kick” -- knocking his chair backwards into a full bathtub. Cobb jolts awake and manages to disarm and incapacitate Saito.
As the explosions and riots outside draw nearer, Cobb explains to Saito that his team gained access to Saito’s mind because of an extramarital affair, and that Saito is still withholding key information from them. Saito responds by telling Cobb that the dream was in fact a failed “audition.” In a train compartment, all the men are revealed to still be asleep. A boy on the train activates a timer and places headphones on Arthur, playing Edith Piaf’s “Non, Je Ne Regrette Rien,” waking Arthur up. In the apartment, Saito notices a difference in the carpeting and realizes they are still dreaming, but thinks it’s Arthur’s dream, not Nash’s. As the rioters burst in, all the men wake up on the train except Saito. Arthur scolds Nash—the dream’s “architect"—for the error in the carpeting. Cobb disembarks at Kyoto, and when Saito finally awakens, only a small boy remains in the compartment, looking innocent.
In a penthouse in Kyoto, Cobb spins a top and tensely holds his gun as he watches it lose momentum. The phone rings and Cobb talks to his children. When they ask where “mommy” is, Cobb says that she is gone. Arthur arrives and suggests to Cobb that Mal’s intrusions in the dreams are getting worse. Cobb tells Arthur that, since they failed to deliver Saito’s expansion plans to a company named Cobol Engineering, they should disappear.
Approaching a helicopter on the roof, Cobb says he will go to Buenos Aires, and Arthur to the United States. In the helicopter, they find Saito waiting for them, having taken Nash captive. Saito explains that Nash turned them in, and offers to let Cobb kill him. When Cobb refuses, Nash is dragged out of the helicopter, to be given up to Cobol.
Christopher Nolan's Inception begins with a dream-within-a-dream—Saito's dream within Nash's dream, to be precise—and the film's every frame asks the viewer to question whether the events unfolding on screen are taking place in the external world or in a dreaming person's mind. The plot and style of Nolan's film intentionally blur the distinction between the world of reality and the world of dreams. In the opening sequence, for example, Mal demonstrates that dreamers can still feel "real" pain by shooting Arthur in the foot. Whereas other filmmakers like David Lynch and David Cronenberg have used dreaming to explore surreal forms, unnatural dialogue, and grotesque imagery, Nolan's dreamworlds are notable for their fluid, seamless sense of continuity with reality. Dreams in the film are often rendered with a degree of hyperrealism, though subject to a particular kind of logic that Cobb explains to newcomer Ariadne.
One tenet of this logic is that dreams always begin in medias res, as the film itself does by opening during a siege that Cobb's team is carrying out in Saito and Nash's dreaming minds. Nolan stages the sequence as a way to introduce the viewer to some of the preliminary rules of "dream-sharing" technology: for example, killing someone in a dream will under normal circumstances wake them up, as will a "kick." Nolan, whose previous films included Batman Begins and The Dark Knight, conceived of Inception as an action-thriller, with heist and science-fiction elements. Within the workings of this genre, dreams become volatile arenas for unpredictable, militaristic battles, as Cobb's team of criminal interlopers attempts to infiltrate the weaponized minds of their hostile targets.
In the film, dreams often adopt a nesting structure of riddles, puzzles, forgeries, and mazes. The opening of the film essentially poses a specific, important puzzle to the viewer—why do Saito and Cobb suddenly look drastically different during their first scene together?—inside of a larger riddle, which is that the entire sequence is taking place inside a two-layered dream. The viewer will later discover that the initial shots of Saito and Cobb sitting together are in fact flash-forwards to Cobb's attempt to rescue Saito from "limbo"—a purgatory-like state where dream-sharers can become stuck. The recursive, non-chronological, labyrinthine structure of the film reflects the "impossible" objects that Arthur will later describe to Ariadne, such as the Penrose staircase.
Nolan represents dreamworlds as hyper-realistic but highly unstable—susceptible to physical collapse and the intrusions of sinister projections like Mal, Cobb's dead wife. Dreams-within-dreams are especially unstable, which Nolan conveys by showing how the tumult of the oncoming riot in Nash's dream causes the mansion to crumble and implode in Saito's dream. Because the "layers" of the dream are unfolding simultaneously, Nolan makes liberal use of an editing technique called cross-cutting to thread together the different planes of concurrent action in a way that is comprehensible to the viewer. To show how these planes of action are transpiring at the same time but at different speeds, Nolan cross-cuts between events unfolding in normal time and events unfolding in extreme slow motion, such as the scene of Cobb falling into the tub as a "kick" to wake up from Saito's dream.
In the opening sequence, Nolan also introduces the viewer to the idea that dreams have architects, in this case Nash. Because Nash forgets to craft the dreamworld with enough attention to detail, he allows Saito to realize that he is dreaming. Many have interpreted Nolan's film as presenting an elaborate metaphor for cinema itself: in the same way that dream-sharing technology allows sleepers to enter a seductive world populated by imagined architecture and fantastical projections, so too does cinema allow film-goers to have a collective experience in a fictional world, elaborately realized by directors and actors. This dreamt world, in Nolan's film as in the filmmaking industry more broadly, is only powerful if it can compel and persuade the viewer to suspend disbelief, which is why a mistake as trivial as Saito's polyester carpet can compromise the integrity of the whole.